**Core Concept:**
Periodontal ligament is a connective tissue that connects the cementum of the tooth to the alveolar bone. It plays a crucial role in maintaining the position, stability, and support of teeth in the alveolar socket. The ligament consists of fibers, cells, and extracellular matrix that allow for limited mobility of teeth and their resistance to traction forces.

**Why the Correct Answer is Right:**
The correct answer to this question is option C, which states that the periodontal ligament has predominantly elastic fibers. Elastic fibers are responsible for providing the ligament with its tensile strength, allowing for the limited mobility of teeth within the alveolar socket while maintaining their stability. The other options are incorrect for the following reasons:

A. Collagen fibers: While collagen fibers are also present in the periodontal ligament, they primarily contribute to its tensile strength rather than its elasticity.

B. Ground substance: Ground substance is the extracellular matrix component that provides space for cells and fibers, but doesn't define the primary function or type of fibers in the ligament.

D. Mixed fibers: The correct answer highlights the predominance of elastic fibers, not a mixed composition of both collagen and elastic fibers.

**Why Each Wrong Option is Incorrect:**
- Collagen fibers: While collagen is essential for tensile strength, its primary role is to provide rigidity and tensile strength rather than elasticity.
- Ground substance: Ground substance is essential for maintaining the spaces for cells and fibers, but it does not define the primary function or type of fibers in the ligament.
- Mixed fibers: The correct answer highlights the predominance of elastic fibers, not a mixed composition of both collagen and elastic fibers.

**Clinical Pearl:**
The elastic fibers in the periodontal ligament contribute to the limited mobility of teeth while maintaining their stability. This understanding is crucial for understanding the normal functioning of the periodontal complex and recognizing any pathological changes, such as in cases of periodontal disease, where the elastic fibers may degrade, leading to increased tooth mobility and loss of attachment.

**Correct Answer:** C. Elastic fibers